It is proposed to develop and exploit a protein cross-linking technique which relies upon the use of a dissociable bifunctional reagent possessing different functional grougs at either end. Cross-linked species may then be characterized or identified using two dimensional gel electrophoresis or other technqiues. This is an ideal method to study the molecular interactions and possible structural relationships between a known protein and other components of a system. A reagent which has these properties, containing an acylating group on one end, a photoreactive group on the other end, and a periodate-cleavable tartaryl group in the middle, has been prepared. Preliminary studies already indicate the utility of this type of compound as a general crosslinking reagent. The proposed studies, which will take advantage of its special properties, would be carried out in several fairly well defined systems currently under investigation at the University of Oregon. These include two complexes of the mitochondrial inner membrane, electroplax acetyl choline receptor, and receptor interactions giving rise to chemotaxis in bacteria.